Optoelectronic packages include an optical engine that is mounted on a package substrate. The optical engine may include a light source (e.g., lasers, light emitting diodes (LEDs), silicon photonics, etc.) and/or photodetectors. Currently available optoelectronic packages generally include an optical engine that is cantilevered over an edge of the package substrate so that transmitting and/or receiving optical fibers may be aligned and coupled with the optical engine.
An exemplary illustration of an optoelectronic package 100 is shown in FIG. 1. As illustrated, the optoelectronic package 100 includes a transmit (Tx) line 110 and a receive (Rx) line 112. The Tx line 110 and the Rx line 112 are represented as blocks, but it is to be appreciated that the lines may each include optical fibers for routing transmitted or received optical signals to or from light sources or photodetectors. Additionally, the Tx line 110 and Rx line 112 may provide multiplexing or demultiplexing functionalities. In FIG. 1, a photodetector 114 is shown at the end of the Rx line 112. Additionally, an integrated circuit 116 for controlling the optical engine may also be mounted to the substrate 105. As illustrated, the fiber block 120Tx that includes the Tx fiber 122Tx may be mounted to the portion of the optical engine that is cantilevered over the edge of the substrate 105. Similarly, the Rx fiber 122Rx may pass through a fiber block 120Rx and be mounted to a portion of the optical engine that is cantilevered over the edge of the substrate 105. While not illustrated in order to not obscure the Figure, it is to be appreciated that the fiber blocks 120 and the optical engine may be secured together with an epoxy in order to prevent movement.
Optical fibers that are employed in optoelectronic packages and systems today require precise alignment. For example, single mode fibers typically have an 8-10.5 μm core size and require alignment on the order of ±1 μm. The optical fibers may pass through a fiber block that may be aligned with the optical engine and fixed in place with an epoxy. Once the desired alignment is achieved, the epoxy is cured and the fiber block is locked in place.
However, after assembly and during use, the alignment of the fibers may shift for a multitude of reasons such as, thermal drift, physical handling, or external sources of vibration coupling into the system. As the alignment shifts, the system degrades and may no longer be operable at the required data rates. Since the fiber block is secured to the package with a cured epoxy, misalignment requires removing the optical system from the package or board and actively realigning the fiber block and reapplying and curing epoxy. Furthermore, cantilevering the Tx and Rx lines 110, 112 over the edge of the substrate 105 induces stress in the optical fibers. Stress in the optical fibers leads to stress induced losses of the optical signal, thereby further reducing the efficiency of the device.